VI EXPLANATION OF PLATES. 



PLATE II. 



ORGANS OF STRIDULATION AND ADDITION OF THE ORTHOPTERA. 



Fig. 1. A, Internal anatomy of a common Green Grasshopper, Stenobothrus 

 virldulus. t, t, are the main tubes of the tracheal', which pass down the line of 

 spiracles or external respiratory openings at either side of the body ; f, t', t', 

 central air bladders with which they are in communication ; m, m', membrana 

 tpnpana, or drum of the organ of audition ; e, an opening suitable to act as an 

 Eustachian tube ; li is a more highly magnified view of the membrana t\Tnpana> 

 m, showing the horny pieces on its disc, the inwardly attached vesicle containing 

 a watery fluid, and the acoustic nerve, n, issuing from beneath it ; e, as before. 



Fig. 2. A, Shows one of the double rimEe or slits in the tibiaj of the forelegs 

 of Locusta viridissima, the great Green-leaf Cricket ; b, shows, m, a membranum 

 tympanum of the auditory apparatus, e.xposed by the removal of the operculum 

 to this ^cavity ; c, e, is a tube of the trachea that penetrates the forelegs of this 

 insect, and swells out into a vesicle opposite the tympana, m ; n is the acoustic 

 nerve attaching itself to the vesicle in a ganglion. (These figures are reduced 

 from Fischer's " Orthoptera Europea.") d, shows the position of e and a, 

 in situ. 



Fig. 3. Acridium migratoria, the Migratory Locust, a, the entrance of the 

 auditory cavity ; the blur, a', b', indicates the movement of the hind leg in stridu- 

 lation ; x and y are the veins on which the lima, or file, is mostly placed. 



Fig. 4. A, Lima of Acheta domesticus, the House-cricket ; B, lima of Gryllus 

 campestris, the Field-cricket (from Landois) ; c, is the file of Locusta viridissima. 

 (All highly magnified.) 



Fig. 5. Anal fields of the wing-covers of Locusta viridissima. a, under sur- 

 face of the anal field of right elytron ; sni, mirror ; s, rounded edge, over which 

 the lima or file, I, on the under surface of the anal field of the left elytron, b, 

 passes during the music. 



Fig. 6. Femoral joint of the hind or leaping legs of the Stenobothrus viridulus, 

 the common Green Meadow Grasshopper, showing the lima or file on the inner 

 side, I, emploj^ed by the insect in stridulating or singing. (Highly magnified.) 



Fig. 7. The lima in Stenobothrus pratorum more highly magnified (from 

 Landois). 



Fig. 8. Right wing-cover of Gryllus campestris, the Field-cricket. Under 

 side, showing the vein carrying the lima or file, I, with which the insect sings ; 

 s, a veinlet raised at the upper side of the el3'tra, over which the lima passes 

 when the wing-covers, or elytra, are rubbed together in the action of stridula- 

 tion ; sm, a little glassy space thought to be the undeveloped counterpart of the 

 mirror of the Leaf-crickets. (Magnified.) 



PLATE III. 



* organs of STRIDULATION OF ORTHOPTERA AND COLEOPTERA, DRUMS AND 

 AUDITORY ORGANS OF THE CICADjE. 



Fig. 1. View of the ventral surface of Geotrupes stercorarius, the common 

 Watchman Beetle. /, Lima on the coxal joint of the hind legs ; s, faint groove. 



